diff --git a/Userland/Libraries/LibWeb/Streams/TransformStreamDefaultController.cpp b/Userland/Libraries/LibWeb/Streams/TransformStreamDefaultController.cpp
index d22a51f320..cd23db1e0f 100644
--- a/Userland/Libraries/LibWeb/Streams/TransformStreamDefaultController.cpp
+++ b/Userland/Libraries/LibWeb/Streams/TransformStreamDefaultController.cpp
@@ -43,6 +43,15 @@ Optional<double> TransformStreamDefaultController::desired_size()
     return readable_stream_default_controller_get_desired_size(*readable_controller);
 }
 
+// https://streams.spec.whatwg.org/#ts-default-controller-enqueue
+WebIDL::ExceptionOr<void> TransformStreamDefaultController::enqueue(Optional<JS::Value> chunk)
+{
+    // 1. Perform ? TransformStreamDefaultControllerEnqueue(this, chunk).
+    TRY(transform_stream_default_controller_enqueue(*this, chunk.has_value() ? chunk.value() : JS::js_undefined()));
+
+    return {};
+}
+
 // https://streams.spec.whatwg.org/#ts-default-controller-error
 WebIDL::ExceptionOr<void> TransformStreamDefaultController::error(Optional<JS::Value> reason)
 {
diff --git a/Userland/Libraries/LibWeb/Streams/TransformStreamDefaultController.h b/Userland/Libraries/LibWeb/Streams/TransformStreamDefaultController.h
index 5d14122b44..e2bef2f2cc 100644
--- a/Userland/Libraries/LibWeb/Streams/TransformStreamDefaultController.h
+++ b/Userland/Libraries/LibWeb/Streams/TransformStreamDefaultController.h
@@ -19,6 +19,7 @@ public:
     virtual ~TransformStreamDefaultController() override;
 
     Optional<double> desired_size();
+    WebIDL::ExceptionOr<void> enqueue(Optional<JS::Value> chunk);
     WebIDL::ExceptionOr<void> error(Optional<JS::Value> reason = {});
 
     auto& flush_algorithm() { return m_flush_algorithm; }
diff --git a/Userland/Libraries/LibWeb/Streams/TransformStreamDefaultController.idl b/Userland/Libraries/LibWeb/Streams/TransformStreamDefaultController.idl
index 9b2859062e..4bb99ac60c 100644
--- a/Userland/Libraries/LibWeb/Streams/TransformStreamDefaultController.idl
+++ b/Userland/Libraries/LibWeb/Streams/TransformStreamDefaultController.idl
@@ -3,7 +3,7 @@
 interface TransformStreamDefaultController {
     readonly attribute unrestricted double? desiredSize;
 
-    // FIXME: undefined enqueue(optional any chunk);
+    undefined enqueue(optional any chunk);
     undefined error(optional any reason);
     // FIXME: undefined terminate();
 };